Remove IO reference from Flutter XlsIO

Author: Sridhar-Sukumar

lib/samples/xlsio/yearly_sales/yearly_sales.dart

@@ -58,7 +58,7 @@ class _YearlySalesXlsIOState extends SampleViewState {
     //Accessing via index
     final Worksheet sheet = workbook.worksheets[0];
     sheet.name = 'Sales Report';
-    sheet.showGridLines = false;
+    sheet.showGridlines = false;
     final Worksheet sheet2 = workbook.worksheets.addWithName('Data');
     sheet.enableSheetCalculations();
 
@@ -265,7 +265,7 @@ class _YearlySalesXlsIOState extends SampleViewState {
 
     sheet.charts = charts;
 
-    final List<int> bytes = workbook.saveStream();
+    final List<int> bytes = workbook.saveAsStream();
     workbook.dispose();
 
     //Launch file.